I just DO it.... But i do it on a computer, not on a Phone.. It is not possible on a Phone.

And when I like the result, I post it here on steemit, in this case with a sort of explanation of how I did it. On the website of the maker of the software you can find more info about this software:

https://www.mediachance.com/ultrasnap/index.html

And I make screenshots of what I do in another program: Snagit, by a company called techsmith:
http://discover.techsmith.com/snagit-brand-desktop/?gclid=EAIaIQobChMIiIzAvtTB2wIVwuFRCh0ZlgQxEAAYASAAEgLqqvD_BwE

This works fast, because I can easily paste these screenshots into my steemit posts!